A novel rotating drum bioreactor (RDB) with the volume of 18 L and 96 L in our previous work has shown the potential for bioleaching processes with high solid concentration. In this paper, a larger ROB with a volume of 703 L was scaled up, and effect of operation condition and baffle parameters on power consumption in the 96 L and 703 L RDBs was investigated. The results showed that the specific power consumption increased with the rotation speed and was insensitive to aeration rate. Meanwhile, the specific power consumption was negatively related to loading coefficient and was positively related to diameter of ROB. It was found that the power consumption increased with the increase of number and width of baffles. The mass transfer performance was most economic, when the 703 L RDB was equipped with 8 baffles with a 0 angle. The mass transfer performance of the 703 L ROB at the same specific power was close to that of a stirred tank bioreactor (STB) commercially used. For the Al2O3 slurry system, the specific power consumption in the 703 L ROB was less than 1/3 of that in the traditional STB with the same diameter. (C) 2013 Elsevier Ltd. All rights reserved.